At this point in time the United States has one of the safest water supplies in the world, but things change. Our water treatment and delivery systems are aging and the demand for water continues to grow with populations of our cities. In the arid west reclaimed or recycled water, is being used to recharge groundwater. In other places waste treatment plants discharge to rivers that supply drinking water systems. Water recycling and reuse while increasing supply is introducing a variety of contaminants into our drinking water that water treatment systems and water regulations were never meant to address. Under the authority of the Safe Drinking Water Act (SDWA), EPA sets standards for approximately 90 contaminants in drinking water including bacteria and disinfection by products. For each of these contaminants, EPA sets a legal limit, called a maximum contaminant level. EPA requires that all public water supplies be tested for this list of contaminants on a regular basis and meet these minimum standards. In addition, EPA sets secondary standards for less hazardous substances based on aesthetic characteristics of taste, smell and appearance, which public water systems and states can choose to adopt or not. Though 90 contaminants is a lot, there are approximately 80,000 chemicals in use in our society and an uncounted number of pathogens.
Drinking water is typically treated with either Chloramine or chlorine both are disinfectants. (Disinfection by products are several of the chemicals tested for in drinking water supplies.) Chloramine is a combination of chlorine and ammonia that is currently considered best technology for controlling the formation of certain regulated organic disinfection byproducts and has come to replace the use of chlorine in many locations. Since the revisions to the clean water act in the past decade chloramine has returned to common use as a distribution system disinfectant after being replaced in 1940’s with chlorine when there were ammonia shortages. Chloramine lowers microbial densities of coliform bacteria, heterotrophic bacteria, Legionella bacteria while minimizing the formation of regulated disinfection by-products. However, these bacteria and the other substances on the primary drinking water list are not the whole story, nor are they the only substances in our water today.
Recycled or reclaimed water is former wastewater (sewage) that has been treated to remove solids and certain impurities, and then is used in irrigation, discharged to surface water that is a source of drinking water or injected into the ground to recharge groundwater aquifers. In order to make our river, lake, stream and ocean water safe for fishing and recreation, the Clean Water Act of 1972 mandated elimination of the discharge of untreated waste from municipal and industrial sources, and the US federal government provided billions of dollars in grants for building sewage treatment plants around the country. Modern treatment plants, usually using sand filtration and chlorination in addition to primary and secondary treatment, were required to meet certain standards. These standards were never designed to render the waste water potable.
Now; however, this water is being mixed with drinking water reserves. As recycled and reclaimed water is added to the water supply through indirect means, the potential for health impacts increases. Varying amounts of pathogens, pharmaceutical chemicals (e.g., hormones from female hormonal contraception and other pharmaceuticals in common usage) and other trace chemicals are able to pass through the treatment and filtering process, potentially causing danger to humans. Certainly, the USGS and US Fish and Wildlife have documented impact to aquatic life in surface water sources. Drinking water standards were developed for natural groundwater, and are not appropriate for identifying contaminants in reclaimed water. In addition to pathogens, and organic and endocrine disrupting chemicals, a large number of compounds may be present in reclaimed water. Today, we do not even have the technology to test for some of these substances at trace levels, and no studies have ever been done to measure the potential for developmental or health impact from chronic low level dosing. The drinking water standards are simply not sufficient for impaired sources or indirect potable reuse. Nonetheless, as the water supply becomes critical in various locations, recycling of water both direct and indirect is taking place and expanding.
Life depends on water and so in stressed areas like California we are beginning to reach for every potential source of water. The existing set of drinking water standards are not comprehensive and do not define safe drinking water potentially containing trace contaminants from modern life. Water supply managers keep finding additional chemicals in toxic concentrations that evade “best available treatment” standards. There is little health effects information on low doses of pharmaceuticals and endocrine disrupters and limited ability to test at trace levels, and yet without hesitation we pump this water into the groundwater basins that represent the largest storage of water available to us. Water suppliers that serve the same people year-round are required to send their customers an annual water quality report (sometimes called a consumer confidence report). However these water supply reports neglect to clearly state where some of this water comes from and note that water is tested for only the primary and possibly secondary drinking water contaminants.